drm/qxl: fix cursor position with non-zero hotspot

The SPICE protocol considers the position of a cursor to be the location
of its active pixel on the display, so the cursor is drawn with its
top-left corner at "(x - hot_spot_x, y - hot_spot_y)" but the DRM cursor
position gives the location where the top-left corner should be drawn,
with the hotspot being a hint for drivers that need it.

This fixes the location of the window resize cursors when using Fluxbox
with the QXL DRM driver and both the QXL and modesetting X drivers.

Signed-off-by: John Keeping <john@metanate.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: stable@vger.kernel.org
Link: http://patchwork.freedesktop.org/patch/msgid/1447845445-2116-1-git-send-email-john@metanate.com
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

drivers/gpu/drm/qxl/qxl_display.c

@@ -375,10 +375,15 @@ static int qxl_crtc_cursor_set2(struct drm_crtc *crtc,
 
 	qxl_bo_kunmap(user_bo);
 
+	qcrtc->cur_x += qcrtc->hot_spot_x - hot_x;
+	qcrtc->cur_y += qcrtc->hot_spot_y - hot_y;
+	qcrtc->hot_spot_x = hot_x;
+	qcrtc->hot_spot_y = hot_y;
+
 	cmd = (struct qxl_cursor_cmd *)qxl_release_map(qdev, release);
 	cmd->type = QXL_CURSOR_SET;
-	cmd->u.set.position.x = qcrtc->cur_x;
-	cmd->u.set.position.y = qcrtc->cur_y;
+	cmd->u.set.position.x = qcrtc->cur_x + qcrtc->hot_spot_x;
+	cmd->u.set.position.y = qcrtc->cur_y + qcrtc->hot_spot_y;
 
 	cmd->u.set.shape = qxl_bo_physical_address(qdev, cursor_bo, 0);
 
@@ -441,8 +446,8 @@ static int qxl_crtc_cursor_move(struct drm_crtc *crtc,
 
 	cmd = (struct qxl_cursor_cmd *)qxl_release_map(qdev, release);
 	cmd->type = QXL_CURSOR_MOVE;
-	cmd->u.position.x = qcrtc->cur_x;
-	cmd->u.position.y = qcrtc->cur_y;
+	cmd->u.position.x = qcrtc->cur_x + qcrtc->hot_spot_x;
+	cmd->u.position.y = qcrtc->cur_y + qcrtc->hot_spot_y;
 	qxl_release_unmap(qdev, release, &cmd->release_info);
 
 	qxl_push_cursor_ring_release(qdev, release, QXL_CMD_CURSOR, false);

drivers/gpu/drm/qxl/qxl_drv.h

@@ -135,6 +135,8 @@ struct qxl_crtc {
 	int index;
 	int cur_x;
 	int cur_y;
+	int hot_spot_x;
+	int hot_spot_y;
 };
 
 struct qxl_output {